Facebook allows targeting of advertisements based on interests, behaviors, location, and demographics. It also allows targeting groups like website visitors, app users, and audiences that look like existing audiences. It also provides a list of companies who can assist with advertising on Facebook. including data brokers who can augment custom audience lists. Additionally, data is available via the API and some app developers collect data from users via their apps, as Global Science Research did (and then sold it to Cambridge Analytica). Similar services are also offered on Instagram.